Backbenchers were left fuming yesterday after pro-EU PM David Cameron opted to protect the hated bedroom tax rather than legally bind the next government to a referendum on British membership of the bosses’ bloc.

A tug of war between the coalition partners erupted after the Lib Dems refused to back the Tory legislation unless the government supported West Cornwall MP Andrew George’s Affordable Homes Bill, which would have chipped away at cuts to benefits for council and social tenants with a spare room.

A visibly furious Mr George rounded on Mr Cameron at Prime Ministers’ questions, accusing him of “abusing the privilege of executive power” by maneouvring to deny “the clear will of this house” and strike down his attempt to reverse the bedroom tax.

“If the Prime Minister wants his EU referendum to proceed then all he needs to do is demonstrate a level of mature engagement,” said the Lib Dem MP, whose Bill passed its second reading by 75 votes last month.

Mr Cameron retorted: “If the honourable gentleman believed in democracy he would recognise that the EU referendum Bill passed this house with a massive majority.”

The PM added that he was “very disappointed” that the Referendum Bill would not now progress, but “people should be in no doubt — if they want an in-out referendum, there is only one way to get it and that is to return a Conservative government.”

It was the second time in 24 hours that the PM had used the phrase in the Commons, prompting speculation that he had deliberately scotched the EU Bill in order to be able to position the Tory Party against the challenge posed by Ukip.

If it had become law, Tory backbencher Bob Neill’s European Union (Referendum) Bill would also have bound a Labour government to hold a vote by 2017 or pass an Act repealing it.

Mr George’s Bill would have rolled back the bedroom tax by exempting carers and specially adapted homes and limiting it to those who had been given a “reasonable offer” of alternative housing.